1. Field of the Invention
The present invention relates to a cardiac function analysis apparatus and method for displaying a cardiac function. Further, the present invention relates to a computer program for the apparatus and the method.
2. Description of the Related Art
Conventionally, in cardiac motion analyses using CT images obtained in a plurality of different phases (temporal phases), slice images (short-axial images) in the short-axial direction of a heart are obtained from a three-dimensional image that has been obtained in each of the phases. Then, outlines R1, R2, R3 and R4 of the cardiac muscle wall in each of the phases are extracted from the slice images at corresponding positions (please refer to FIG. 8A, which is a diagram illustrating a heart in diastole (relaxation period), and FIG. 8B, which is a diagram illustrating the heart in systole (contraction period)). Then, outlines R1 and R3 of the cardiac muscle wall (inner surface) at a cross section on a line intersecting the same position of long axis L are obtained. Further, a difference between the outlines R1 and R3 is used as an amount of the motion of the cardiac muscle wall (please refer to FIG. 8C). This processing is performed at each position of short-axial cross sections that are orthogonal to the long axis of the heart from the cardiac apex to the cardiac base. Then, the obtained result is output as a three-dimensional analysis result.
Further, as a method for displaying such a cardiac motion analysis result, a bull's-eye display method has been used. In the bull's-eye display method, when a heart is assumed to approximate an ellipsoid model, the result is displayed by concentrically arranging sliced planes that have been obtained by slicing the ellipsoid at constant intervals in a direction traversing the long axis of the ellipsoid. This display method is mainly used for function images. Further, this display method is used to display images directly obtained by cardiac muscle scintigraphy (SPECT; single photon emission computed tomography) and functions obtained from the result of analysis using CT (computed tomography) or MRI (magnetic resonance imaging) (for example, U.S. Patent Application Publication No. 20050008209).
When the aforementioned result of analysis is obtained by using the CT or MRI, the motion of the heart in a radial direction from the center of the short-axial image of the heart is observed. However, the actual motion of the heart includes rotation and twisting motion in addition to relaxation and contraction. Therefore, the aforementioned result of analysis does not reflect the function of the heart based on the actual motion of the heart.